An Organic Light Emitting Display (OLED) is a type of flat panel display based on a matrix of organic light emitting pixel elements. OLEDs have the potential to provide image qualities comparable to conventional CRT displays, and yet, they are light weight and can be built on flexible substrate. But, because the light intensity of each pixel is determined by the properties of the organic-light-emitting-element for that pixel, it is difficult to make OLEDs with uniform display intensity. The variations of the display intensity is due to the variations of the display characteristics of all organic-light-emitting-elements. The variations of the display characteristics are inevitable, because large numbers of organic-light-emitting-elements have to be manufactured over a very large area. It is important to improve the display uniformity, if one want to make OLEDs with large number of gray levels, such as 256 levels for each color.
In this document, the applicant present a new method, which the applicant claims to solve the uniformity problem of OLEDs once for all. The new method provides almost perfectly uniform display properties for OLEDs regardless the inevitable variations of each organic-light-emitting-element. The new method disclosed in this document is performed in three steps: First, the display characteristics of every organic-light-emitting-element in the display is measured. Second, the correct driving parameters for each organic-light-emitting-elementxe2x80x94used as calibration parameters directlyxe2x80x94are calculated and stored in a calibration memory as a complete look-up table, or the calibration parameters for each organic-light-emitting-element are calculated and stored in a calibration memory as a partial look-up table. Third, using the complete look-up tables or using partial look-up tables in combination with additional calculation, the correct driving parameter for any organic-light-emitting-element with any luminosity level can be obtained, and the correct driving parameters are used to drive the OLED. For the first step described above, the display characteristics of all organic-light-emitting-elements can be measured in a dark chamber by turning on one organic-light-emitting-element at a time. For the second step described above, linear approximation or other higher order approximation can be used. For the third step, there are two general embodiments: (1) with embodiment one, all the calculated correct driving parameters are stored in a video memory and the driver electronics use these calculated correct driving parameters in the video memory to drive the display; (2) with embodiment two, the desired light intensities are stored in a video memory without any compensation, and using the complete look-up tables or using partial look-up tables in combination with additional calculation, the driver electronics calculate the correct driving parameters by fetching the light intensities from the video memory and use these calculated correct driving parameters to drive the display directly. For both embodiments mentioned above, when partial look-up tables are used, additional calculations are needed to obtain the correct driving parameters, and these calculations can be performed by the main microprocessor or a dedicated display processor.
It is an object of the invention to provide a method that can provide almost perfectly uniform display properties for OLEDs regardless the inevitable variations of each organic-light-emitting-element.
Additional advantages and novel features of the invention will be set forth in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention maybe realized and attained by means of the instrumentality and combinations particularly pointed out in the appended claims.
To achieve the foregoing and other objects and in accordance with the present invention, as described and broadly claimed herein, a measurement method is provided to measure the display characteristics of every organic-light-emitting-element in the display, a calculation method is provided to obtain the calibration parameters of any given organic-light-emitting-element by using the measured display characteristics of the corresponding organic-light-emitting-element as the raw data, a calibration memory is provided to store the calibration parameters for any given organic-light-emitting-element as a complete look-up table or as a partial look-up table, a method is provided to obtain the correct driving parameters for any given organic-light-emitting-element for any give light intensity by using the complete look-up table without additional calculation or by using the partial look-up table with additional calculation, and finally a driver electronics is provided to drive the display with the correct driving parameters. For the measurement method provided to measure the display characteristics of every organic-light-emitting-element in the display, a dark chamber can be used. An OLED driven by the correct driving parameters will provide images free of intensity distortions caused by each organic-light-emitting-element""s property variations.